E-Flora BC: Electronic Atlas of the Flora of British Columbia

Silybum marianum (L.) Gaertn.
milk thistle (blessed milkthistle)
Asteraceae (Aster family)

Introduction to Vascular Plants

© Jamie Fenneman  Email the photographer   (Photo ID #10792)

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Distribution of Silybum marianum
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Species Information

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Annual or biennial herb from a fibrous root; stems erect, solitary, simple or few-branched, ridged, glabrous to sparsely woolly-hairy, 0.5-1.5 m tall.
Basal leaves lacking; stem leaves elliptic below, becoming oblanceolate or lanceolate above, alternate, spiny-toothed, pinnately lobed, 15-80 cm long, 5-30 cm wide, veins lighter in colour thus leaves appearing white-mottled, stalked below, becoming unstalked above with conspicuous ear-like flanges, clasping at the bases.
Heads discoid, terminating the branches; involucres 2-6 cm wide; involucral bracts narrowly egg-shaped, margins spiny, tips spiny but basally expanded; ray flowers lacking; disk flowers purple.
Achenes elliptic to egg-shaped, 6-7 mm long, flattened, dark brown with a narrow, yellow, apical collar, glabrous; pappus with numerous bristles, these deciduous in a ring.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Mesic to dry roadsides and disturbed areas in the lowland zone; rare on SE Vancouver Island and the adjacent mainland; introduced from the Mediterranean region.

Source: The Illustrated Flora of British Columbia


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Carduus marianus L.
Mariana mariana (L.) Hill

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References